This invention relates to reinforced polymers, more particularly to molded polyurethane and/or polyurea polymers which contain a particulate filler material, which has excellent distinctness of image (DOI).
It is well known to employ various filler materials to modify the physical properties of polymeric materials. The use of such fillers is thoroughly described, for example, in Handbook of Fillers and Reinforcements for Plastics, Katz et al., eds., Van Nostrand Reinhold Company, New York, 1978. These fillers usually perform at least one of two major functions. Certain fillers (reinforcing fillers) improve certain desirable physical properties of the polymer, especially tensile strength and flexural modulus (stiffness). These reinforcing fillers typically, although not always, have an aspect ratio significantly greater than one. Examples of these include, fiber glass, milled glass, flaked glass, certain wollastonites, other high aspect ratio minerals polymeric fibers, metallic fibers, and the like. Other fillers are used simply as extenders to reduce the overall cost of the polymer composition. These extenders are typically characterized by their very low cost, and often have an aspect ratio close to one, which causes them to have minimal reinforcing properties. These include kaolin, silica, calcium carbonate, and the like.
In recent years, filled molded polymers, particularly filler polyurethane and/or polyurea polymers have replaced metals in an increasing number of applications. Of particular interest are certain automotive applications, especially automotive exterior body parts. Filled polymers offer several advantages in these applications, particularly their ability to withstand minor impacts, such as encountered in low speed collisions, without damage and the fact that they do not rust. The filled polymers used in making these body parts must exhibit a demanding combination of physical properties. They must have good thermal properties over a wide temperature range, have good dimensional stability, be rigid enough to bear their own weight, yet be flexible enough to withstand minor impact without damage, and be relatively unaffected by extremes in weather conditions. Good success in meeting most of the foregoing criteria has been achieved by using certain reinforced polymers. However, one area in which filled polymers are often lacking is in surface quality. Metals provide a characteristically mirror-like surface after painting. Unfilled polymers often approach or equal the surface qualities of metals, but reinforced or extended polymers usually are significantly inferior in this respect. Because surface appearance is of major importance to the consumer, it is highly desirable to provide a polymeric material having improved surface qualities, and other desirable physical properties.
Similarly, there are other applications wherein excellent surface appearance in a filled polymer is desired. Accordingly, it would be desirable to provide a filled polyurethane and/or polyurea polymer having excellent surface qualities.